Scope
Replaces an existing block with a mechanic that does nearly the same thing

Suggestion
Remove all fertile soil types, but add the ability for dispensers to plant saplings/seeds/other crops.
Make this configurable/data-packable to allow adding crops/trees from other mods.

Justification
The existing fertile soil blocks don't work very well (see #93, #73) and it's difficult to add new crop types, mainly due to many plants in the game using different logic to decide what they can be planted on.
They also act as a one-block 'free resources' source (creating seed potatoes from nothing, for example), and are limited to vanilla crops (see #32, #90).
Switching to a configurable dispenser-based system would allow fixing all of these issues.
The dispenser should be able to target both the air-block above soil or the soil block itself, to allow still having fields of crops by having upwards-facing dispensers under the soil.

Impact
This will make automatic farms rather harder to make, as you now actually need to handle replanting instead of crops replanting themselves by magic.
However, it means far more crop types will be farmable, and still achieves the original goal of adding a consistent, reliable (ie- not villager-based) method of replanting for a wide variety of crops.
This would be a breaking change, as it removes a block type.